The prior art appreciates that substituted imidazolines can be prepared by reacting aminoethyl ethanol amine with carboxylic acids. Because fatty acids are not particularly selective in their reaction with aminoethyl ethanol amine between the primary and secondary amine functions, the fatty acid can react with the aminoethyl ethanol amine with either the primary amine or the secondary amine. As a consequence, appreciable amounts of diamide result as a side reaction product. The diamide so produced and the equation illustrating the reaction are theoretically as follows: ##STR1## where R is as herein below defined.
The diamide by-product is undesirable because the diamide is inert, insoluble in water, and precipitates thereby causing objectionable turbidity in a final product produced by opening a substituted imidazoline ring in the presence of sodium chloroacetate.
In addition to the unwanted diamide, the indicated prior art process for making substituted imidazolines apparently also has inherently associated with it a tendency to produce a byproduct ester having a characteristic detectable infrared peak at 5.75 microns. The exact reaction causing the production of this ester is not certain, and the structure of this ester is likewise not certain, but it is theorized that this ester may have the structure: ##STR2## where R is as herein below defined. We wish to point out that we do not wish to be bound herein by theory.
The presence of such an ester in a substituted imidazoline product is particularly undesirable when such product is to be reacted with sodium chloroacetate and converted into a surfactant composition with amphoteric properties for the reason that the ester when present tends to reduce the foamability of a product which is undesirable from the standpoint of commercial practicality. So far as is known, prior art processes for making substituted imidazolines do not provide steps to permit one to produce a product imidazoline composition containing less than two weight percent imidazoline.
Consequently, the art needs a new and improved process for making substituted imidazolines in high purity.